The lack of that feature keeps me on VI Pro as well. I wish they would support that mode in Synchron Player, at least as an option. Most sample players behave the same way VI Pro does, and many electronic keyboardists rely on that feature for performance.
This is what Paul told on another thread about the auto-trill request:
"Regarding the Synchron Player Legato: I'm afraid the internal logic won't allow to play these "auto-trills" when you hold down one note and then trigger another."
"This is not the question of adding a feature... I have been told that it is technically impossible."
Anyway, hope they can understand how important this feature is, and assuming that the Synchron Player will someday be improved, that this should be on the top list of things to implement.